Furnace conveyer structure



Dec. 14, 1954 D. T. SIEGEL 2,696,978

FURNACE CONVEYER STRUCTURE 3 SheetsF-Sheet 1 "Filed May 6, 1950 INVENTOR.

aami/w Dec. 14, 1954 D. 'r. SlEGEL FURNACE CONVEYER STRUCTURE 5 Sheets-Sheet 2 Filed May 6, 1950 lllll En INVENTOR.

pm/ad Wei W Dec. 14, 1954 D. T. SIEGEL 2,696,978

FURNACE CONVEYER STRUCTURE Filed May 6, 1950 5 Sheets-Sheet 3 L1 AZ 5 ,1? INVENTOR.

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United States Patent 2,696,978 FURNACE CONVEYER STRUCTURE David T. Siegel, Glencoe, 111. Application May 6, 1950, Serial No. 160,420

9 Claims. (Cl. 263-8) This invention relates to furnaces and more particularly to an electrical furnace and improved conveyors to be used in conjunction therewith.

It is an object of the present invention to provide an improved furnace for heating objects carried on a continuous conveyor; more specifically it is an object of the invention to provide an improved high temperature furnace for use in baking vitreous ceramic coatings such as enamel and the like on articles.

Another object of the invention is to provide, in a furnace of the type described, an improved conveyor in which the loading and unloading stations are at substantially the same, point so that one operator can adequately run the furnace. I Y

Yet another object is to provide, in a furnace of the type described, an improved conveyor which can be readily removed from the furnace without dismantling the furnace or the conveyor.

in connection with the foregoing, it is another object to provide an improvedconveyor in a furnace of the type described in which the portion of the conveyor carrying the incoming articles is arranged with respect to the portion of the conveyor carrying outgoing articles in a manner as tov permit heat transfer between the incoming and outgoing articles and thereby conserveheat.

Still another object of the invention is to provide an improved mounting for articles on a conveyor of the type set forth in which rotation of the articles with respect to the furnace is obtained by movement of the conveyor..

7 In connection with the foregoing object'it is another object of the present invention to provide an improved means for positioning the article support on the conveyor and means for stopping the conveyor in the event that an article support is improperly positioned thereon.

A further object of the invention is to provide an improved furnace of the type described which is so constructed and arranged as to be more economical in operation by conserving heat and to be more economically and easily installed, serviced, and repaired. 1 r

These and other objects of the invention will be apparent from the following specification when taken in conjunction with the accompanying drawings. Inthe drawings wherein like reference numerals have been used to designatelikeparts throughout: t a

rFigure l isa side elevational'view of a furnace and its associated conveyor made in accordance with and embodying the principles of thepresent invention;

"Figure 2 is a partial perspective View of the furnaceand conveyor shown in 'Figure l as seen from the loading and unloading station of the conveyor, one of the article supportsfbeing shown diagrammaticallyin a position just after removal from the conveyor; 1 i

Figure 3 is a'partial-enlarged plan viewof the conveyor as seen at the loading and unloading end;

Figure 4 is a vertical cross-sectional view of the conveyor-support and drive substantially as seen in the directions of the arrows along the line 4-4 of Figure 3;'

'Figure' S is a 'perspective'view of an article support'useil in the present invention with an article thereon, the article illustrated being a resistor; a p T Figure 6 is anenlarged cross-sectional view of the supg tir't and re'sis'tor 'shown in Figure 5-substantiallyas s n ant-r dire tion. or *fth an-ewe elongate: line? 6 furnace being broken away to better illustrate the structure thereof;

Figure 8 is a partial side elevational view similar to Figure 7 of the end of the conveyor disposed within the heating portion of the furnace;

Figure 9 is a vertical cross-sectional view of the conveyor substantially as seen in the direction of the arrows along the line 9-9 of Figure 7; and t Figure 10 is a schematic drawing of the electrical circuit used in the present invention. 7

Referring to the drawings and particularly to Figures 1 and 2 thereof, there is shown a furnace, generally designated by the numeral 20, which is made in accordance with andembodies the principles of the present invention.

Furnace 20 comprises generally a preheating section 22, a high temperature section 24, a conveyor 26 for articles to be heated, and a motor 28 and gear reducer 30 which drive the conveyor 26.

The preheating section 22 and the high temperature section 24 are mounted upon a frame which is preferably formed of angle irons. The frame includes a plurality of side bars 32, 34, and 36 which'cooperate with bars 38, and 40, disposed substantially perpendicularly thereto, to form supports for the sections 22 and 24. The frame is in turn supported by a plurality of legs 42, 44, and 46, which are of such a length that the axes of the sections 22 and 24 are inclined with respect to the horizontal supporting surface 48, the preheating section 22 being disposed lower than the high temperature section 24. A tray 50 is mounted on the frame underneath the portion of conveyor 26 which extends outwardly from section 22. Tray 50 is provided with an upstanding lip 52 and is supported by a brace 54 extending from the free edge of tray 50 to the side bar 32 of the frame. Tray 50 is positioned to collect the hot articles and material dropping from conveyor 26 and prevents these heated particles from falling on the mechanisms and structure therebelow. 1

Both the preheating section 22 and the high temper ature section 24 are surrounded by suitable refractory bricks 56 which provide the necessary strength, insulation, and temperature resistance. High temperature section 24, in addition, carries a coating of insulating material 58 which is disposed about the bricks therebeneath. The rear end of high temperature section 24, the end disposed to the right in Figure 1, is provided with a sliding door 60 which provides access to the interior for cleaning, servicing, and repairing. Normally door 60 remains in the closed position during operation.

Disposed above and below the portion of the conveyor 26 disposed in high temperature section 24 of the furnace is a pair of heating elements 62 and 64. The heating elements 62 and 64 are preferably of the electrical resistance type and are connected in the electrical circuit in the manner shown in Figure 10. The heating element 62 is disposed above the conveyor 26, shown in dotted lines in Figure 1, in a position to most effectively heat articles on the uppermost portion of the conveyor, and heating element 64 is disposed below conveyor 26 in a position to most effectively heat articles positioned on the lower portion of the conveyor. The high temperature section 24 connects directly with the preheating section 22, the aperture therebetween being substantially equal to the internal cross section of the preheating sec- P tion 22.

The forward end of the preheating section 22, i. e. the end disposed to the left as viewed in Figure 1, is provided with a collector 66 which has attached thereto an upwardly extending pipe 68. The collector 66 and the pipe 68 provide an exhaust for removing moisture and fumes from the entire furnace 20. Generally the natural convection current induced by the heated masses of air being displaced by cold masses of air is sufficient to provide the necessary ventilation for furnace 20. If more positive ventilation is desired, a fan can be installed to provide a forced draft and, in addition, air inlets may be formed in the furnace 20 to give 'greatervolurnes' of ci e 'a'i -fl, I Tl'ip forward or"left"end*iof preheating section 22 is providedwith a Ver'ticaIlj'SlidiIigdoor 70'having a handle "72 thereomf aging and lowering the door; Door 701's 3 provided on either side with tracks 74 and 76 which provide vertical guideways for the door when it is moved upwardly or downwardly. The end of preheating section 22, on which door 70 is mounted, is the end of section 22 through which the conveyor 26 enters. I

The conveyor 26 comprises generally a pair of longitudinally extending side frame members 78 and 80 which extend substantially the full length of conveyor 26. As is best illustrated in Figures 3 and 9, the frame members 78 and 80 are substantially rectangular in cross section, and the ends thereof disposed outside of the preheating section 22 are provided with rectangular longitudinally disposed recesses extending a short distance therein. These rectangular recesses receive bars 82 and 84, respectively, which may be adjustably positioned therein by means of set screws 86 and 88 respectively.

The outer ends of bars 82-84 carry bearings 90 and 92 in which is disposed a transversely extending axle 94 which is rotatably mounted therein. The bearings 90-92 are preferably formed in two parts and are held together by bolts 95 and 96 which have nuts 98 and 100 threadedly engaged therewith to clampingly hold the bearings 90 and 92 in assembled relationship about axle 94. The right hand end of axle 94, as viewed in Figures 3 and 4, extends outwardly and beyond bearing 92 and receives thereon a wheel 102 which is adapted to be driven by a belt 104, which is in turn driven from an output pulley 106 of gear reducer 30. i v v I Mounted on axle 94, inside of the bearings 90-92 and adjacent thereto, are a pair of driven sprockets 1'03 and which have teeth formed on the periphery thereof adapted to engage a flexible chain. Also mounted on axle 94 and positioned inwardly with respect to the sprockets 108 and 110 are a pair of disks 112 and 114 which serve as safety devices to prevent the gloves, sleeves or other portions of the clothing of the operator from being entangled with the sprockets 108-110 andfthe chains which are to be described hereinafter. The sprockets 108-110 and the disks 112 and 114 are suitably secured to axle 94 in such a manner that these members rotate when axle 94 is rotated.

The rear ends of the frame members 78-80, i. e. the ends disposed within the high temperature section 24 of the furnace 20, carry and have rotatably mounted therein axle 116. A pair of externally toothed sprockets 118 are fixedly mounted on axle 116 inside of the frame mem bers 7 8-80.

As can be clearly seen in Figure 3, two continuous endless chains generally designated by the numerals 120 and 122 are carried and driven by the sprockets 108-118 and the sprockets 110-118 respectively. The chains comprise a plurality of two types of links 121 and 123 which are arranged alternately around the entire length of the chains. Mounted on and preferably formed integral with each ofthe links 121 is a vertically upstanding plate 124 which has an elongated slot 126 formed therein, the axis of the slot being disposed normally with respect to the direction of travel of the associated chain. -It is seen, therefore, that each chain 120-122is provided onalternate links thereof with plates 124, the links of each chainwhich carry plates 124 being aligned.

The tension in chains 120 and 122 is adjusted by loo'sening the set screws 86-88 and movin'gth'e bars 82-84 inwardly or outwardly with respectto the frame members 78-80 respectively. If a link in the chains must be replaced, or repaired, tension in the chains is relieved by loosening set screws 86-88 and shoving the bars 82-84 into their respective recesses.

7 Means is provided for removing the entire conveyor from the furnace without dismantling the furnace or conveyor in the form "of a pair of U-shaped guide and support members 128 and 130. The support members 128-130 are attached to the frame of the furnace and are positioned with the open side of the cross section thereof disposed inwardly, and with the legs of the cross section disposed horizontally. The conveyor frame members '78 and 80 are disposed within the channels of support members 128 and 130 respectively, and are adapted to, slide therein. Support members 128 and 130 extend substantially the entire length of the conveyor 26, but terminate a short distance from the position of the set screws 86-88. The-conveyor frames 78-80 are fixedly positioned within the sup'po rt mefmbers 128-130 by means of set screws 132 and 134, respectively, which are mounted on the support members 128-130 and bear against the sides of the frame members 78-80. To remove the conveyor 26 from the furnace 20, the set screws 132-134 are loosened, the "drive belt interconnecting the drive wheel 102 and the drive pulley 106 is removed, and the frame members 18-80 are pulled out of their respective members 128-130. This ready withdrawal of the conveyor from the furnace makes service, repair, and replacement of the conveyor unusually simple. The conveyor is reinserted in the furnace by merely pushing the frame members 78-80 into the support members 128-130 and thereafter tightening the set screws 132- 134. After the drive belt 104 has been replaced, the furnace is again in readiness for operation. it will be seen that the time the furnace is inoperative for purposes of repair will be minimized with this construction.

The chains 120 and 122 are preferably formed of a heat and temperature resistant metal since the chains will be exposed to the high temperature in section 24. in order to help carry the relatively great weight of the chains and to insure that the chains travel in substantially the same path each time, a pair of chain supports 136 and 138 are provided for the chains 120-122 respectively. The chain supports 136-138 are mounted upon one arm140-142 of brackets 144-146, the brackets 144-146 being suitably secured to the frame members 78-80 respectively. As is best seen in Figure 9, the chain supports 136-138 extend under the chains 120-122 respectively, the supports extending substantially the full length of the conveyor but terminating just short of the sprockets 108, 110, and 118.

Means is provided for supporting articles to be heated on the moving conveyor 26. The article support, as may be best seen in Figures 5 and 6, comprises generally a cylindrical rod 148, whose length is greater than the distance between the chains 120-122 and whose diameter is slightly less than the width of slots 126 in plates 124 mounted on the chains 120-122. A wheel is mounted on rod 148 toward one end thereof and 'is attached thereto. Wheel 150 has a groove 152 extending around the circumference thereof, as may be best seen in Figures 3, 4, and 9.

The conveyor 26 is adapted to receive thereon and carry the article supports. More specifically the slots 126, in opposed plates 124 on chains 120-122, are adapted to receive the opposite ends of rod 148 whereby to support and carry rod 148. An article support is mounted on the conveyor 26 by first inserting the end of rod 148 disposed farthest from wheel 150 in the slot 126 of a plate 124 mounted on chain 122. Rod 148 is pushed through the slot until the end of rod 148 disposed adjacent wheel 150 can be inserted in the slot 126 of an opposed plate 124 on chain 120.

The rod 148 is centered on conveyor 26 in such a manner that the groove 152 in wheel 150 engages the lower member 154 of a guide track. As may be best seen in Figures 3 and 4 the guide track section 154 is so positioned horizontally with respect to the conveyor 26 that the rod 148 is aligned with respect to chains 120-122. Engagement of wheel 150 with track memher 154 causes rotation of wheel 150 and its associated rod 148. Any articles mounted on rod 148 will also be rotated. As will be explained more fully hereinafter, the track member 154 extends substantially the entire circumference of the conveyor 26, and therefore serves to cause rotation of rod 148 and its associated article throughout substantially the entire length of the conveyor. Rotation of the articles about the axis within the furnace is desirable and often advantageous in certain heating applications, such as when firing vitreous enamel coatings.

Referring to Figures 7, 8, and 9, it will be seen that an upper track member 156 is provided to engage the top of the groove 152 in wheel 150 after the wheel has passed beyond the door 70 and into the preheating section 22 of furnace 20. By providing both upper and lower track members 154-156, the wheels 152 are positively prevented from leaving the track and are therefore guided throughout the length of conveyor 26. The track members 154 and 156 are curved downwardly at the end of conveyor 26 which is disposed within the high temperature section 24 whereby to follow the path of the article supports around the sprocket 118. Referring again more specifically to Figure 7, it will be seen that the track members 154 and 156 continue along the lower side of the chain 120 whereby to guide the article supports as they movefr'omthe furnace and'out'to Ethe loading and unloading endof the conveyordisposed out side of furnace 20. The lower sections of trackmembers 154-156 end beforethe article supports reach the forward sprocket 108. ,No guide tracks engage the wheels 150 on the article supports as they move "around sprocket 108. This structure is necessary in order tofacilrtate application and removal of the article supports from the conveyor 26 e :Means is provided for mounting the track members 154 and 156 on the frame member 78 in'the form of the bracket 144. Bracket 144 has an inwardly extending portion 158 which has extending laterally therefrom in opposed directions a pair of arms 160162. Arm 160 supports the 'upper sectionof the lowertrack member 154 and arm 162 supports the lower section of the track member 154. A pair of brackets 164 (see Figure 7) and 166 (see Figure 9), serve to support, the upper section and the lower section respectively of the upper track member 156. Additional supports not shown are preferably provided within high temperature section 120 to provide supports for these tracks at the rear end of conveyor 26.

Referring to Figure 9, it will be seen that track 154, in addition tolaterally positioning rod 148, alsovertically positions rod 148 in such a manner that the rod is disposed in the upper portion of its associated sl et-126. In order to mount rod 148 substantially horizontally, a guide support 168 is provided at the end of rod 148 disposed toward chain 122. Guide support 168 serves to hold this end of rod 148 in the upper end of its associated slot 126, thereby to maintain rod 148 in substantially a horizontal position. Maintaining rod 148 in a sub stantially horizontal position is important in most applications since thearticle supported thereon is free to slide along the axis thereof. If the rod 148 were not positioned substantially horizontally, the article thereon would tend to move to one end or the other of rod 148 and might interfere with the proper operation of conveyor 26. Guide support 170 is providedbeneath the lower section of conveyor 26 and performs the same function as guide support 168. The guide supports 168170 are mounted on the frame member 80 by arms 172 and 174 respectively of bracket 146. v t Means is provided for detecting the position of the rods 148 in plates 124 and indirectly the positioning of wheel 150 on its associated guide track member 154. The detecting means is effective to stop the motion of the conveyor 26 if one of the rods 148 is misaligned. The detecting means comprises a pair of switches176and 178 which are mounted on brackets 180 and 182 respectively, the brackets 180-182 being mounted on the support members 128130. Switches 176-J78 are provided with piv tal swit h arms 184-186 respectively, the switch arms being positioned on either side of conveyor 26 in such a manner that a properly positioned and aligned rod 148 passes therebetween without contacting the arms. If rod 148 is positioned too far to the left or right as viewed in Figure 9, one of the ends of rod 148 will contact either switch arm,.184 or switch arm 186.

Referring now to the wiring diagram shown'in Fi ure 10, the manner in which switches 176 and 178 are effective to stop conveyor 26 will be explained. Electrical potential is obtained from two lines designated L1 and L2 respectively. The drive motor 28 has one terminal thereof connected to L2 and the other terminal is con nected through a solenoid operated switch 188 .and a manual switch 190 to line L1. Solenoid operated switch 188 is normally c osed when its associated solenoid 192 is deener ized. The operation of' motor 28-,is normally controlled by the manual switch 190.'. When the switches 188 and 190 are closed or energized and openative. one terminal of the solenoid 192 issc onnected to line L2 andthe other terminal of solenoid '192 .is connected thr u h inspecti switches 17,6'178 oline L1. The switches ,176 and 178 are disposed in parallel so that the solenoid 192 will be energized if either switch is closed. Normally, switches 176 and 178 are in the open position whereby to -deenergize solenoid 192. and .close 'switch 188. If one of therods 148 is misalignedso'jthat onefofiits ends contacts switch .arm. 184Lor 186. :the circuit""to solenoid 192 will be close'd and switch-188 will beop rod'148, which hascaused' the interruption of motor 28, and the conveyor will then be in condition to continue. Switch 188 is'preferably of the type which must be manually reset after being opened, whereby to prevent the conveyor 26 from being run while the operator is repositioning the misaligned rod 148. p

The manner in which heating current is supplied to the heating elements 62 and 64 is also illustrated in Figure 10. One of the terminals of the heating elements is connected through connection 194 to line L1, and the other terminal of the heating elements is connected through switch 196 to line L2.

The present invention is particularly suited for'baking vitreous enamel coatings on articles such as the resistor 198, shown in Figures 5 and 6 of the drawings. It is to be understood that the furnace may be used for other purposes, but that it has particular applicability in this use. The resistor 198 is generally cylindrical in shape and has an aperture 200 extending longitudinally therein.- Aperture 200 is slightly greater in diameter than the diameter of rod 1.48 whereby rod 148 can be inserted therethrough as shown in Figure 5. Generally the resistor 198 is provided with terminal lugs 202 which project radially therefrom.

In forming vitreous enamel coating on resistors and the like, the base, which in the case of a resistor will be wound with a resistor wire, is dipped in the enameling mix and then dried. The coating of enamel mix must then be heated to a relatively high temperature, whereby to fire the coating to form vitreous enamel. A furnace, such as furnace 20 of the present invention, is particularly suitable for the firing operation.

Operation of the furnace 20 and conveyor 26 is as follows. The dipped articles such as the resistors 198, are mounted on the article supports by inserting rod 148 through an aperture therein, such as the aperture 200 in resistor 198. Rod 148 is then mounted on the conveyor 26 by inserting the ends thereof in the slots 126 in plates 124 on the chain's -122. Since the rod 148 is longer than the distance between the opposed plates 124, the end of rod 148 disposed away from wheel and beyond the resistor 154 is first placed in slot 126 of a plate 124 in chain 122. Next the end of rod 148, disposed adjacent wheel 150 is placed in the slot 126 of a plate'124 in chain 120. The axis of rod 148 is disposed substantially perpendicularly to the direction of travel of the chains 120122 if the proper plates 124 oneach of the chains are chosen. The articles are positioned on the conveyor at the end of the conveyor shown in Figures 3 and 4, i. e. the end ofthe conveyor disposedoutside of the furnace 28. This end of conveyor 26 will hereinafter be called the loading and unloading end.

Switch 196, controlling the current to heaters 62-64, is closed and the temperature of the furnace is brought up to the proper firing temperature for the enamel coating applied. After the furnace has reached the proper temperature, switch 90 controlling motor 28 will be closed and motor 218 will be energized, thereby to rotate drive wheel 102 and sprockets 108110. The motor 28, gear reducer 30, and associated parts are so arranged that the upper section of the conveyor moves into the preheating section 22 and the lower section of the conveyor moves out of the preheating section 22.

Articles suchas the resistors 198 are placed on the article supportrods 148 and these rods are then mountedon the conveyor in the manner described above. The rate of travel'of the conveyor is relatively slow so that an operator can place the article support rod 148 in the support plates 124 while the conveyor'is in motion. If the operator has properly positioned the rod 148 so that wheel 150 engages the track 154. in groove 152 of the wheel,'the article will move into the. preheating sec- 'tion 22' between the inspecting switches 176178 since the switches are positioned outwardly with respect to the ends of rods 148. After rod 148 passes the switches 176-178, the upper track member 156 engages theupper side of groove 152 of wheel 150 and positively holds wheel 150 on the track.

Ifthe' rod 148 ismisaligned','o'ne of the switch arms .184 1 86 of switches 176-178 wil be contactedand its associated switch closed. fAshas' been described above, frilosing ither switch 176 -178 'isYelfect-iveto op'en -the e 1 c'u'it' df motbi' 28"and= thereby 'stop inoyement 'of eonveyast ztiwi Ttre eperator may thenx pfioperly align-"itthe misaligned article and can resume operation of conveyor 26 by resetting switch 188.

The temperature in the preheating section 22 is generally lower than the firing temperature but any moisture such as surface moisture will be evaporated and the articles will be gradually heated. The contact between wheel 150 and the track members 154-156 will cause rotation of the rod 148 and its associated part 198. The article will be continuously rotated throughout substantially the entire length of the conveyor 26. As the articles pass from the preheating sections 22 into the high temperature section 24, they encounter increasing temperatures until when they are disposed adjacent the heating elements 6264 they will be subjected to the firing temperature. The speed of conveyor 26 is so adjusted that the articles remain in the firing zone for the necessary length of time. Since the articles are being continuously rotated, all surfaces thereof will be uniformly and therefore adequately fired.

When the article supports and their associated article reach the rear end of conveyor 26 adjacent sprocket 118, the direction of travel will be reversed and they will be gradually withdrawn from the high temperature section 24 into the preheating section 20. It is to be noted that the track members 154-156 are curved around sprocket 118 whereby to continually rotate and guide the article support during this portion of its path of travel.

As the hot fired articles move along the lower portion of conveyor 26, they will be disposed adjacent the cooler incoming articles positioned on the upper portion of conveyor 26. This arrangement permits heat transfer between the hot and the cold articles and thereby effects a conservation of heat.

The fired articles pass from the preheating section 22 and finally beyond the ends of the guide track members 154156. The article support and its associated article are then ready for removal from the conveyor. The articles are still relatively hot and accordingly a suitable utensil such as the pair of pliers 204, shown in Figure 2, are preferably used to remove the article and its associated support. After the fired article has been removed, an unfired article may be positioned on the conveyor in its place and thereby a firing cycle for a new article is initiated.

From the foregoing description of operation, it will be seen that a single position can be used for both loading and unloading the articles and their associated supports on the conveyor 26, thereby to enable one operator to successfully operate the furnace. By providing means for rotating the articles such as the wheels 150, a uniform and well fired vitreous enamel coating is obtained. A great saving in heat is obtained due to the construction of the conveyor, since the outgoing hot fired articles transfer appreciable portions of their heat to the cold incoming unfired articles. Heat is further conserved by positioning the furnace 20, and its associated conveyor 26, at an angle with respect to the supporting surface 40, thereby to cause the naturally lighter hot air to move toward the hot high temperature section 24. This structural feature, in cooperation with suitable insulation, effects a considerable saving in heat.

Means has also been provided to insure that the articles are rotated in the form of the detecting circuit which stops operation of conveyor 26 in the event that the rotating wheel is not disposed on its track 154156. In addition to insuring the quality of the fired vitreous enamel coating, this feature prevents possible injury to the conveyor or the furnace by jamming or otherwise abnormally interrupting the motion of the conveyor.

As has been explained above, the conveyor can be rapidly and easily removed from the furnace for inspection, repair, servicing, or replacement of parts. To remove conveyor 26 from the furnace, the motor 28 is first turned off, the drive belt 104 is removed, and the setscrews 132-434 are loosened. The frame members 78--80 of the conveyor 26 are then free to be pulled outwardly and away from the associated support and guide members 128130. It is to be noted that conveyor 26 is inclined in such a position with respect to the horizontal, that gravity will aid in withdrawing the conveyor from the furnace.

It will be seen therefore, that there has been provided .a furnace and conveyor which will fulfill all the objects and advantages set forth above. Although .a preferred embodiment \of the invention has been shown for purposes of illustration, it is to be understood that various changes and modifications can be made therein without departing from the spirit and scope of the invention. Accordingly, the invention is to be limited only as set forth in the following claims.

The invention is hereby claimed as follows:

I. A furnace comprising a heating chamber having an opening in one side thereof, heating elements mounted in said chamber for supplying heat to said chamber, a conveyor arranged to convey articles into and out of said chamber through said one side, means for driving said conveyor, means for mounting articles to be heated on said conveyor, means operative when contacted by said mounting means for continuously rotating said articles when the articles are within said heating chamber, guide means adapted to engage said mounting means throughout a portion of said conveyor to hold said mounting means in operative position with respect to said rotating means, and detecting means arranged and constructed to stop said conveyor if said mounting means do not properly engage said rotating means.

2. In a furnace, a conveyor comprising spaced apart frame members, rotatable axles mounted on said frame members, endless conveyor members mounted on said axles and adapted to be driven thereby, means formed on said conveyor members for supporting objects to be conveyed thereby, and support members mounted in said furnace, said support members being adapted slidably to receive and support said frame members whereby to allow said conveyor to be withdrawn from said furnace Without dismantling said furnace or said conveyor.

3. In a furnace, a conveyor comprising a pair of spaced apart frame-members, axles mounted on said frame members, endless conveyor members mounted on said axles and adapted to be driven thereby, removable article supports mounted on and carried by said conveyor member, track means positioned adjacent said conveyor and adapted to engage and rotate said article supports when said conveyor members are driven, and detecting means operative to stop said conveyor if said article supports do not properly engage said track means.

4. In a furnace as claimed in claim 3, wherein the detecting means is disposed exteriorly of at least one side of the conveyor members in position to engage an article support not in proper position transversely of the conveyor members to be rotated by said track means.

5. In a furnace, a conveyor comprising spaced apart frame members, axles rotatably mounted upon said frame members, endless conveyor members mounted on said axles and adapted to be driven thereby, article supports including a rod and a grooved wheel fixedly mounted on said rod, holding means formed on said conveyor members to receive and support said rod for rotation and permissive transverse shifting movements, and a track disposed adjacent said conveyor and positioned to engage within groove of said wheel whereby to rotate said article support and the article thereon when said article sup port is moved by said conveyor and prevent lateral displacement of the article supports when the wheel and track are interengaged, said track terminating at the open end of the furnace to permit transverse shifting of the rods facilitating attachment to and removal from the conveyor.

6. In a furnace, a conveyor comprising spaced apart frame members, axles rotatably mounted upon said frame members, endless conveyor members mounted on said axles and adapted to be driven thereby, article supports including a rod and a wheel fixedly mounted on said rod, means formed on said conveyor members to rotatably receive and support said rod, a track disposed adjacent said conveyor and positioned to engage said wheel where by to rotate said article support and the article thereon when said article support is moved by said conveyor, and detecting means mounted to engage said article support and operative to stop said conveyor if said wheel does not properly engage said track.

7. In a furnace, a conveyor comprising a pair of spaced apart frame members, a pair of adjustable extension members mounted on one end of said frame members, a rotating axle mounted on the end of said frame members opposite said one end, .an axle rotatably mounted on said extension members, endless conveyor members supported on and rotated by said axles, that portion of the conveyor members adjacent the axle .on said extension members forming .both a loading and an unloading station, means mounted adjacent the axle on said extension member to form a shield around the conveyor at the point where the axle on said extension members engages said conveyor member, and article supports mounted on and adapted to be conveyed by said conveyor members.

8. In a furnace, a conveyor comprising a pair of spaced apart frame members, axles mounted on said frame members, endless conveyor members mounted on said axles and adapted to be driven thereby, article supports mounted on and carried by said conveyor members, an inner track means positioned adjacent said conveyor and adapted to engage and rotate said article supports when said conveyor members are driven, and an outer track means spaced away from said inner track means and aligned therewith, said outer track means extending around at least a portion of the path of travel of said conveyor members to hold said article supports in engagement against said inner track means.

9. In a furnace, a conveyor comprising spaced apart frame members, axles rotatably mounted upon said frame members, endless conveyor members mounted on said axles and adapted to be driven thereby, article supports including a rod and a wheel fixedly mounted on said rod, means formed on said conveyor members rotatably to receive and support said rod, an inner track disposed adjacent said conveyor and positioned to engage said wheel to rotate said article support and the article thereon when said article support is moved by said conveyor, and an outer track spaced away from said inner track and aligned therewith, said outer track extending around a portion of the path of travel of said conveyor and positioned to hold to said wheel against said inner track.

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